When evaluating sensorineural hearing loss, it can be difficult to determine if the origin of the hearing loss is cochlear or retrocochlear, meaning beyond the cochlea.

The SISI hearing test was designed to assist in differentiating between cochlear or retrocochlear hearing loss. The short increment sensitivity index is a measure of intensity discrimination that assesses an individual’s ability to recognize an increase in intensity during a series of pure tone bursts. These increases are presented in 1 dB increments and the individual is asked to respond when they detect an intensity change.

The SISI audiology test can be used in conjunction with acoustic reflexes to help determine the nature of sensorineural losses. Patients with a cochlear disorder will be able to differentiate the 1dB steps, whereas an individual who has a retrocochlear disorder will not. 

A continuous tone is presented at the test frequency and at a sensation level of 20dB above the pure tone threshold for that frequency. Every 5 seconds a short 1dB increment is super-imposed over the continuous tone for approximately 200msec. The client is asked to signal to the examiner that they have detected an incremental increase. The possibility of false positives or false negatives is reduced by the interspersion of 5dB increments after every five test presentations. These 5 dB increases can be used initially to condition the patient to the task, and provide a check for understanding and accuracy. After the presentation of 20 test increments, a percentage score can be derived by multiplying the number of increments by five. 

Results can be interpreted as: 

70%-100% correct = high (cochlear loss) 

20-70% correct = inconclusive 

<20% = low (retrocochlear loss)